Relearning Everything

Hello Greg!

Congratulations on your career adaptability!

I am also working on a Arcuino - DCC - stepper motor railway turntable.  What scale is your railroad?

Tom

#H&WTR

#ModelRailroad

@hayttom

Hi Tom, I am an HO modeller. The turntable is relatively small, about 9" actual length. The prototype was in Woodstock, NB Canada. Being a newbie, I chose a motor that seemed to have decent holding torque. It's an NEMA17 – 73oz.in 17HS8401. I'd like to program in the stops rather than have sensors. Thinking simplicity over hardware. 

Hi Greg,

I've found your website - that will give me some fun reading tonight.

I'm also programming my turntable stops but I think I'll need one sensor for initial homing - though it has occurred to me that if I always shut my system down with the turntable at a known position, homing might not routinely be necessary.

(I'm also Canadian, but I'm living in Kyiv.)

Tom

Glad to see you here and maybe we can both share some stuff learned here back at Model Railroad Hobbyist!

@photo-bud

Nice to see a familiar face!

Hi to you all, i am Peter from the Netherlands. My model railroad scale is OO, I started a long time ago with N-scale, switched to HO while everything became too tiny for my eyes. And during a holiday in Llangollen, Wales, I decided that I had enough of all the continental stuff. At every exhibition you see the same stuff running around. A small prairie was bought in Chester and some wagons at the Dapol factory. A big thing on the wish list was also a small turntable to rotate this locomotive and the ones to come.

While these fully functional turntables are expensive I decided to go for the a Peco manual type in combination with a stepper motor. That's when I discovered the arduino's. Knowing nothing about programming these things. Just hooking up the wiring was clear to me.

I found a program that suits for me on Rudy's ModelRailroad site working with push buttons and a NEMA17.

The only thing I would like to add to this program is the smooth acceleration and deceleration when the turn table starts and reaches it's point where I want it to stop. 

I think the accelstepper library is what I need to introduce into my sketch but I do not have a clue how to use it. Or is this far too complicated for my low level of experience with arduino's and programming?

By the way at the moment the turntable is running perfectly in a prototype set up. A MDF board with an MDF bridge, a 6 wire slipring on the stepper driving the bridge. The zero point finder is made with a Hall sensor and a neodyne magnet on the bridge. The turntable has 4 stopping points ( 3 to go to the loco shed and maintenance area and 1 for turning around the locos to get their chmneys at the front side). The stepper motor runs with microstepping at 1600 steps per rotation via an A3967 easydriver board. I am using the Arduino Uno.

Below is the code I am using.

#define NUM_POSITIONS 4
#define ENABLE_PIN A0 // LOW = driver enabled
#define M1_PIN A1 // M1 microstepping mode
#define M2_PIN A2 // M2 microstepping mode
#define DIR_PIN A3 // to DIR pin of driver
#define STEP_PIN A4 // to DIR pin of driver
#define POTM_PIN A5 // Used to change speed
#define POS_1_PIN 9 // LOW = go to pos 1
#define POS_2_PIN 8 // LOW = go to pos 2
#define POS_3_PIN 12 // LOW = go to pos 3
#define POS_4_PIN 11 // LOW = go to pos 4
#define ZERO_PIN 6 // LOW = start find zero routine
#define ZERO_FOUND_PIN 7 // LOW = zero switch found
#define ONOFF_LED_PIN 13 // Motor running LED
#define DIR_LED_PIN 4 // Motor direction LED
#define PULSES_PER_REV 200 // Pulses per revolution

// Define number of positions, and steps from zero to each position
unsigned long tt_position[NUM_POSITIONS + 1] = {0,400,800,1200,1600};

byte dir, current_pos, new_pos, rpm, rpm_old;
unsigned long timeoflaststep;

#include <EEPROM.h>

void motor_enable() {
digitalWrite(ENABLE_PIN, LOW); // LOW = driver enabled
digitalWrite(ONOFF_LED_PIN, HIGH);
digitalWrite(DIR_PIN, dir);
}

void motor_idle() {
digitalWrite(ENABLE_PIN, HIGH); // HIGH = driver disabled
digitalWrite(ONOFF_LED_PIN, LOW);
}

void find_zero() {
Serial.println("Finding zero sensor");
dir = 0;
motor_enable();
while(digitalRead(ZERO_FOUND_PIN) == HIGH) {
if ((micros() - timeoflaststep) > stepinterval()) {
timeoflaststep = micros();
digitalWrite(STEP_PIN, HIGH);
// delayMicroseconds(10); // only needed if step pulse is too short to be detected
digitalWrite(STEP_PIN, LOW);
}
}
motor_idle();
Serial.println("Zero sensor found");
Serial.println();
current_pos = 0;
new_pos = 1;
}

unsigned long stepinterval() { // calculates step timing based on potmeter input
rpm = map(analogRead(POTM_PIN), 0, 1024, 1, 21) * 10; // max 200 rpm, else pulses get lost
if(rpm != rpm_old) {
Serial.print("RPM: ");
Serial.println(rpm);
rpm_old = rpm;
}
return 60000000UL / PULSES_PER_REV / rpm;
}

void rotate(unsigned int numsteps) {
Serial.print("moving to pos ");
Serial.print(new_pos);
Serial.print(" pulses ");
Serial.print(numsteps);
Serial.print(" dir ");
Serial.println(dir);
motor_enable();
while(numsteps > 0) {
if ((micros() - timeoflaststep) > stepinterval()) {
timeoflaststep = micros();
digitalWrite(STEP_PIN, HIGH);
// delayMicroseconds(10); // only needed if step pulse is too short to be detected
digitalWrite(STEP_PIN, LOW);
numsteps--;
}
}
motor_idle();
Serial.print("pos ");
Serial.print(new_pos);
Serial.println(" reached");
}

void setup() {
pinMode(ZERO_PIN, INPUT_PULLUP);
pinMode(ZERO_FOUND_PIN,INPUT);
pinMode(POS_1_PIN, INPUT_PULLUP);
pinMode(POS_2_PIN, INPUT_PULLUP);
pinMode(POS_3_PIN, INPUT_PULLUP);
pinMode(POS_4_PIN, INPUT_PULLUP);
pinMode(M1_PIN, OUTPUT);
pinMode(M2_PIN, OUTPUT);
pinMode(DIR_PIN, OUTPUT);
pinMode(STEP_PIN, OUTPUT);
pinMode(ENABLE_PIN, OUTPUT);
pinMode(ONOFF_LED_PIN, OUTPUT);
pinMode(DIR_LED_PIN, OUTPUT);
digitalWrite(M1_PIN, HIGH); // set M1,M2 to 1,1 for microstepping
digitalWrite(M2_PIN, HIGH);
motor_idle();
current_pos = EEPROM.read(0);
if(current_pos > NUM_POSITIONS) {
current_pos = 1;
EEPROM.write(0,1);
}
new_pos = current_pos;
Serial.begin(9600);
Serial.println();
Serial.print("Current memory position = ");
Serial.println(current_pos);
Serial.println();
Serial.println("If memory position is NOT according");
Serial.println("to reality, then find zero first!");
Serial.println();
}

void loop() {

stepinterval(); // read speed and show RPM on serial monitor

if(digitalRead(ZERO_PIN) == 0) find_zero();
if(digitalRead(POS_1_PIN) == 0) new_pos = 1;
if(digitalRead(POS_2_PIN) == 0) new_pos = 2;
if(digitalRead(POS_3_PIN) == 0) new_pos = 3;
if(digitalRead(POS_4_PIN) == 0) new_pos = 4;

if(new_pos != current_pos) {
if(new_pos > current_pos) {
dir = 1;
rotate(tt_position[new_pos] - tt_position[current_pos]);
}
else {
dir = 0;
rotate(tt_position[current_pos] - tt_position[new_pos]);
}
current_pos = new_pos;
EEPROM.write(0, current_pos);
}
}

Thanks robotBuilder,

I will notice that for a next code upload.